Barrow Island fact file

Description

Barrow Island was formed around 8,000 to 10,000 years ago as rising sea-levels separated it from mainland Australia (1)(2). Located approximately 60 kilometres off the north-west coast of Western Australia, Barrow Island is the second largest island in the state (2). Much of the island is covered by spinifex grasslands which provide important habitat for a variety of wildlife (3). While the main feature of Barrow Island’s geography is the undulating limestone uplands, the island is surrounded by a mixture of sandy beaches and rocky shores, low cliffs, dunes, salt flats and reefs (2)(4)(5).

A network of humid caves can be found under the surface of the island, some of which extend up to 100 metres underground (2). These provide a home for some of the island’s varied subterranean species, including species of eel, snake and blind fish (5).

The landscape of Barrow Island is arid and the climate is usually hot and dry. Most of the annual rainfall occurs during the cyclone season between November and April, and amounts to around 320 millimetres per year (2)(3).

Barrow Island was declared a public reserve for flora and fauna in 1908, and has been classified as a ‘Class A’ Nature Reserve since 1910 (6).

Range

Barrow Island covers an area of approximately 234 square kilometres and is around 25 kilometres long and 10 kilometres wide (1)(2).

Biodiversity

Due to its isolation from mainland Australia and protection afforded under its statutory status, Barrow Island is one of the most important conservation reserves in Western Australia. Nearly 2,800 species have been recorded on Barrow Island, including at least 24 endemic animal species and subspecies found nowhere else on Earth (7).

Mammals

Barrow Island is home to 13 species of mammal, including a variety of marsupials as well as native rats, mice and bats. With no introduced predators such as foxes or cats on the island, and a lack of competition from species such as rabbits and cattle, Barrow Island is a haven for some species threatened on mainland Australia (8). Some mammals such as the burrowing bettong or ‘boodie’ now only remain on a few isolated islands like Barrow Island, having been driven to extinction on the mainland (9).

Reptiles and amphibians

43 species of terrestrial reptiles have been recorded on Barrow Island, including a variety of dragons, legless lizards, geckos, skinks, snakes and monitors. Perhaps the most notable is the perentie, the second largest lizard in the world and Barrow Island’s top predator (2)(12). In terms of marine reptiles, Barrow Island’s coastline provides important sea turtle rookeries, particularly for green turtles and flatback turtles which come ashore to nest over the Australian summer months between November to February (2)(5)(12). Sea snakes are also commonly seen in the shallows surrounding Barrow Island (11).

Although arid, Barrow Island also supports one species of amphibian, a desert burrowing frog called Main’s frog, a species able to maintain a state of torpor underground during the dry season (12).

Fish and invertebrates

There is a rich variety of marine and terrestrial invertebrate life on Barrow Island. Between 2004 and 2006 an intensive survey recorded a total of 2,200 terrestrial invertebrate species on the island, including many believed to be new to science (7)(13).

The waters surrounding Barrow Island are protected within marine conservation reserves. The Barrow Island Marine Park was designated in 2004, and is home to an estimated 9,000 species including a great diversity of corals, fish and other marine species (7).

Plants

A total of 378 native plant species have been recorded on Barrow Island, and much of the landscape is dominated by spinifex grassland (7).

Invasive species

As with all isolated ecosystems, one of the biggest threats to island biodiversity is the introduction of invasive species. This is one of the leading causes of species extinction on islands, as native species often lack the adaptations necessary to cope with the introduction of predators or competitors (14). Introduced black rats were discovered on Barrow Island in 1990, but have since been eradicated thanks to a successful baiting programme (15).

Explore Barrow Island’s biodiversity

Natural resources

Oil was discovered on Barrow Island in 1964 and the island is now Australia’s largest operating onshore oilfield (6)(16). The introduction of an oil industry on Barrow Island naturally raised environmental concerns, and because Barrow Island is such an important conservation area, the extraction of oil by Chevron Australia is now only permitted under a Department of Environmental Protection licence. While the oilfield brought with it many potential risks, including damage to the island’s habitats, disturbance from lights, noise and chemicals, and the presence of people and motor vehicles, strict environmental, safety and health standards and procedures were put in place in order to safeguard the environment and minimise the impact on the island ecosystem.

The Gorgon gas field was discovered in deep water west of Barrow Island in 1980. After years of planning, approval to build and operate a liquefied natural gas plant on the island was granted in 2009. As with the development of the oilfield, strict environmental conditions were applied to the Chevron-operated Gorgon Project to limit the impact on Barrow Island’s wildlife (5)(6); for example, the location of the plant on the island was specially selected to avoid disrupting areas of particular conservation significance (17). Three of the main environmental concerns in relation to the Gorgon Project were the potential impacts on nesting marine turtles, the potential quarantine implications associated with the introduction of non-indigenous species to the island, and the dredging of marine channels to create access for large ships. To address these concerns, Chevron Australia established three independent expert panels to provide advice on each issue and help to minimise the impact of the project on the island (5)(17).

Since the Gorgon Project commenced, the level of human and vehicle activity on Barrow Island has increased, and a number of measures have been implemented to safeguard the island’s fauna. These include the introduction of site speed limits, using buses to limit the number of vehicles on the road, installing warning signs and conducting driver fauna-awareness training. Before clearing any sites on the island, trapping and relocation of fauna is conducted. Furthermore, exclusion fences are erected around hazardous areas (17).

Quarantine Management System

Undoubtedly one of the biggest conservation success stories on Barrow Island is Chevron Australia’s Quarantine Management System (QMS) to prevent the introduction of harmful invasive species and diseases to the island (17). By preventing unauthorised visits and carefully monitoring the movement of goods, materials, equipment and personnel, Chevron Australia has been able to provide effective protection for the island’s biodiversity (16)(17).

The Gorgon quarantine management system has been acknowledged by the Western Australian Environmental Protection Authority as likely to be world’s best practice. It pioneers a new, risk-based quarantine approach, with an inter-related set of more than 300 procedures, specifications, checklists and guidelines and is the world’s largest non-government quarantine initiative (17).

The QMS has received a number of accolades including the Business Award for Best Practice Program from the United Nations in June 2012 (17).

a diverse group of mammals characterised by their reproduction, in which gestation is very short, and the female typically has a pouch (marsupium) in which the young are raised. When born, the tiny young crawls to the mother’s teats, where it attaches and stays for a variable amount of time, while it continues to develop. Marsupials also differ from placental mammals in their dentition.

Raptor

bird of prey.

Subspecies

a population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.

Subterranean

living underground, in caves or groundwater

Torpor

a sleep-like state in which the body processes slow to a fraction of their normal rate.

Morris, K.D. (2002) The eradication of the black rat (Rattus rattus) on Barrow and adjacent islands off the north-west coast of Western Australia. In: Veitch, C.R. and Clout, M.N. (Eds.) Turning the Tide: The Eradication of Invasive Species. Proceedings of the International Conference on Eradication of Island Invasives. IUCN Species Survival Commission, IUCN, Gland, Switzerland and Cambridge, UK.

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